Allium Cepa is a homeopathic medicine prepared from the common red onion (Allium cepa) using a specialized homeopathic dilution and potentization process. In homeopathic practice, it is traditionally used for upper respiratory complaints, particularly when symptoms resemble those caused by cutting an onion—profuse watery nasal discharge, frequent sneezing, and irritated eyes.

Homeopathic practitioners may consider Allium Cepa for individuals experiencing the early stages of a common cold, seasonal allergies, hay fever, sinus irritation, or laryngitis when the overall symptom picture matches the individual. It is commonly associated with a watery, irritating nasal discharge, excessive sneezing, nasal congestion, and watery eyes. Symptoms are often aggravated in warm rooms and may improve in cool, fresh air.

Prepared according to recognized homeopathic manufacturing standards, Allium Cepa is selected according to the totality of an individual's symptoms rather than a specific medical diagnosis. Like all homeopathic remedies, it is prescribed based on individualized homeopathic principles.